My goal is to debug my programm, that uses java mail library(including javax.mail and com.sun.mail). So i decided first to download java mail sources and compile it with option -g. I go to the java mail sources and binaries , downloaded them. Somehow sources store in jar but not just zip. Ok. Then i decided to decompile jar into zip with JAD plugin in eclipse. After decompiling i receive empty directory. I downloaded jad.exe and run it , but it throwed a message : JavaClassFileParseException: Not a class file. It says it decompiles only classes, but what about jars? Is it so hard just store sources in fu** zip ???!!!!